As is well known, extrusion dies are subject to various stresses tending to destroy them or, at least, shorten their effective life. For example, in conventional extrusion the internal pressure that is generated during the extrusion process, or during start-up, tends to rupture the die. This effect is traditionally compensated for by manufacturing the die with a relatively thick die wall and/or by shrink-fitting the die into a binding ring which generates compressive pre-stresses at the bore tending to compensate for the stresses developed during extrusion. Naturally, this latter technique is limited to pre-stress values which are less than the compressive yield strength of the material used to make the die.
Unfortunately, in hydrostatic extrusion where the material to be extruded is under such extreme pressure as to cause it to flow plastically, the need to grip the workpiece and force it into the die places an upper limit on the thickness of the wall that can be used in the die. See, for example, the apparatus disclosed in U.S. Pat. No. 3,740,985 which issued June 26, 1973 to F. J. Fuchs, Jr. and which is assigned to the assignee of the instant application. Also, the limitation that the compressive pre-stress generated by the binding ring cannot exceed the compressive yield strength of the die material makes prior art solutions to premature die failure useless for hydrostatic extrusion processes.